Methods and Apparatus for Security Device Portal Sensing

ABSTRACT

A security device, according to various aspects of the present invention, detects movement of a provided portal cover. The security device includes a sensor, a bias magnet, and a processor. The sensor provides indicia of a magnitude of a magnetic flux through the sensor. The bias magnet provides the magnetic flux through the sensor. The processor detects a change in the magnitude of the magnetic flux outside an upper boundary and a lower boundary of a first threshold and a second threshold respectively. The sensor does not move with respect to the magnet. Movement between the sensor and the portal cover changes the magnitude of the magnetic flux through the sensor. The processor determines an average value of a series of values of the indicia of the magnitude of the magnetic flux that fall within the upper boundary and the lower boundary of the first threshold. The upper boundary and the lower boundary of the first threshold and the second threshold respectively are set in accordance with the average value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 60/874,996 filed Dec. 16, 2006 hereinincorporated by reference and U.S. Provisional Application No.60/897,785 filed Jan. 26, 2007 herein incorporated by reference.

FIELD OF THE INVENTION

Embodiments of the present invention relate to apparatus for monitoringaccess to a secured area through a portal.

BACKGROUND OF THE INVENTION

Conventional security devices have been used to control access to asecured area. Access control includes detecting unauthorized ingressand/or egress; authenticating authorized users, providing reports ofingress and/or egress; and providing timely notice of unauthorizedaccess. A security device that controls access to an area may benefitfrom fast, efficient deployment into the area and detection of tamperingwith the security device by an unauthorized person.

SUMMARY OF THE INVENTION

A security device, according to various aspects of the presentinvention, detects movement of a provided portal cover. The securitydevice includes a sensor, a bias magnet, and a processor. The sensorprovides indicia of a magnitude of a magnetic flux through the sensor.The bias magnet provides the magnetic flux through the sensor. Theprocessor detects a change in the magnitude of the magnetic flux outsidean upper boundary and a lower boundary of a first threshold and a secondthreshold respectively. The sensor does not move with respect to themagnet. Movement between the sensor and the portal cover changes themagnitude of the magnetic flux through the sensor. The processordetermines an average value of a series of values of the indicia of themagnitude of the magnetic flux that fall within the upper boundary andthe lower boundary of the first threshold. The upper boundary and thelower boundary of the first threshold and the second thresholdrespectively are set in accordance with the average value.

A method, according to various aspects of the present invention, detectsmovement of a portal cover. A security device performs the method. Themethod includes, in any practical order, (1) averaging a series ofvalues of indicia of a magnitude of a magnetic flux through a sensorthat fall within an upper and a lower boundary of a first threshold toprovide an average value; (2) detecting indicia the magnitude of themagnetic flux that falls outside an upper and a lower boundary of asecond threshold; (3) adjusting the upper and the lower boundary of thefirst threshold and the second threshold respectively in accordance withthe average value; and (4) providing a signal in accordance withdetecting. A magnet couples to a body of the security device to providethe magnetic flux through the sensor. The sensor couples to the body.The sensor does not move with respect to the magnet. Movement of thesensor with respect to the portal cover changes the magnitude of themagnetic flux through the sensor.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the present invention will now be further described withreference to the drawing, wherein like designations denote likeelements, and:

FIG. 1 is a functional block diagram of a security device according tovarious aspects of the present invention;

FIG. 2 is a functional block diagram of a removal detector according tovarious aspects of the present invention;

FIG. 3 a plan view of the security device of FIG. 1 having animplementation of the removal detector of FIG. 2 in a removed position;

FIG. 4 a plan view of the security device of FIG. 1 having animplementation of the removal detector of FIG. 2 in a coupled position;

FIG. 5 a plan view of a bias device and a sensor of the removal detectorof FIG. 2 in a removed position;

FIG. 6 a plan view of a bias device and a sensor of the removal detectorof FIG. 2 in a coupled position;

FIG. 7 a plan view of a bias device and a sensor of the removal detectorof FIG. 2 in a removed position;

FIG. 8 a plan view of the security device of FIG. 1 having animplementation of the removal detector of FIG. 2;

FIG. 9 a plan view a sensing axis of a sensor of the removal detector ofFIG. 2;

FIG. 10 a plan view of the security device of FIG. 1 having animplementation of the removal detector of FIG. 2 in a removed position;

FIG. 11 a plan view of the security device of FIG. 1 having animplementation of the removal detector of FIG. 2 in a coupled position;

FIG. 12 is a functional block diagram of a portal sensor according tovarious aspects of the present invention;

FIG. 13 a plan view of the security device of FIG. 1 having animplementation of the portal sensor of FIG. 12 in a position distal froma portal cover;

FIG. 14 a plan view of the security device of FIG. 1 having animplementation of the portal sensor of FIG. 12 in a position proximateto a portal cover;

FIG. 15 is a data flow diagram of a method performed by security deviceof FIGS. 1, 8, and 12;

FIG. 16 is a diagram of indicia of a magnetic flux, a drift threshold,and an alarm threshold of the portal sensor of FIG. 12 over time;

FIG. 17 is a diagram of an average value of the indicia of magnetic fluxof FIG. 16;

FIG. 18 is a plan view of the security device of FIG. 1 positioned on aportal cover having a right portal cover and a left portal cover;

FIG. 19 is a plan view of an implementation of the security device ofFIG. 1 positioned as shown in FIG. 18;

FIG. 20 is a plan view of an implementation of the security device ofFIG. 1;

FIG. 21 is a plan view of an implementation of the security device ofFIG. 1 having a track that permits sensor movement;

FIG. 22 is a plan view of an implementation of the security device ofFIG. 1 that provides a signal through a portal cover;

FIG. 23 is a perspective plan view of the security device of FIG. 1having an implementation of a coupling apparatus according to variousaspects of the present invention;

FIG. 24 is a perspective view of the coupling apparatus of FIG. 23;

FIG. 25 is a perspective view of the security device of FIG. 23 having acoupling apparatus;

FIG. 26 is a plan view of the security device of FIG. 1 having animplementation of a coupling apparatus according to various aspects ofthe present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A security device, according to various aspects of the presentinvention, secures an area accessible through a portal (e.g., doorway,window opening, hatch, vent) against unreported ingress and/or egress(e.g., access). A security device monitors a portal to provide reportsof ingress and egress; a warning of unauthorized access; authenticationof authorized users; and status of the security device.

A security device detects physical stimulus (e.g., electrical, magnetic,pressure, movement, temperature, light, electromagnetic radiation),physical quantities, physical characteristics, and/or a change in aphysical quantity or characteristic to detect access to the secured areathrough a portal. For example a security device may detect changes intemperature, magnetic flux, motion, pressure exerted against an object;and light (e.g., intensity, wavelength), and radio frequency signals. Asecurity device may detect changes (e.g., increase, decrease, averagevalue, rate of change, departure from a quiescent value) in physicalstimulus as indicia of access to the secured area. A security device maydetect physical quantities of heat, light, vibration, and magnetic flux.

A security device may provide a warning of unauthorized access includinga loud noise (e.g., siren, alarm, bell, human operator voice),transmitting a signal, receiving a signal, transmit a message, receive amessage, and establishing communication with an authorized user (e.g.,monitoring service). The security device may determine a type of warningaction in accordance with a policy or a decision by a human operator.Lack of authorization may be detected by a failure to provide userspecific information (e.g., pin, access code, employee id number), timeof access (e.g., outside of regular working hours), location of access(e.g., access to a particular site rarely or never authorized); time torespond (e.g., slow response from user, response before required), andtype of response (e.g., user enters distress code).

A security device may authenticate users. Authentication may compareuser provided information with information maintained by the securitydevice or knowledge of a human operator. User information may include apin, biometric information (e.g., voice, iris, fingerprint, voicepattern, facial recognition), a password (e.g., a one-touch device, usersupplied password, Dallas/Maxium “one-touch”), a phone number, anemployee number, a bar code, and an RFID transmission. User informationmay be authenticated locally or transmitted to a remote location forauthentication.

Status of the security device may include an amount of battery charge, aremoval event, component health, physical stimulus detected, amounts ofphysical stimulus detected, and variations of physical stimulus. Aremoval event may include moving, shaking, or striking the securitydevice without authorization. A security device may provide notice ofthe status of the security device. Notice may include transmitting asignal (e.g., radio transmission, flashing LED), transmitting a message(e.g., phone message, email, text message), and producing a noise (e.g.,siren, alarm, bell, beep). Notice may include status information (e.g.,amount of battery charge, receive signal strength, transmit signalstrength, occurrence of a removal event, type of removal event).

A security device may provide information (e.g., report, summary,statistics) concerning access to the secured area. A report may includetime of access, date of access, user information, security device statusinformation, physical stimulus detected, notice provided, warningprovided, policy implemented, and actions taken by a human operator. Asecurity device may provide a report according to a policy (e.g.,weekly, monthly, concurrent with notice of unauthorized access) or uponrequest.

For example, security device 100 of FIGS. 1-26, according to variousaspects of the present invention, monitors access to a secured areaaccessible by a portal by monitoring a portal cover and detectingremoval of the security device. Security device 100 may include one ormore portal sensors 102, one or more removal detectors 104, zero or moremotion sensors, access control 110 and zero or more communicationmodules 112.

A portal sensor detects ingress and egress through a portal to and froma protected area. A portal sensor detects physical stimulus, physicalquantities, physical characteristics, and/or a change in a physicalquantity or characteristic. A portal sensor may detect movement of aportal cover (e.g., door, window) as an indication of access through aportal. A portal sensor may report an event. Events may include greaterthan threshold amount of movement of a portal cover (e.g., opening,closing), greater than threshold duration of a portal cover in aparticular position (e.g., open, closed, partially open), greater thanthreshold speed and/or acceleration of portal movement, and greater thanthreshold amount of force applied to the portal and/or the port cover(e.g., attack, destruction).

A removal detector detects removal of the security device from alocation. A location includes position and/or orientation of thesecurity device. A removal detector detects physical stimulus, physicalquantities, physical characteristics, and/or a change in a physicalquantity or characteristic. Physical stimulus used to detect a removalmay include movement in a direction, vibration, change of a physicalforce, a change in orientation, and acceleration of the security device.A removal detector may detect an event (e.g., removal, replacement). Aremoval detector may report an event.

A removal detector may couple a security device to a surface. Couplingincludes coupling a removal detector to a surface using a same physicalstimulus monitored by the removal detector to detect removal. A surfaceincludes a portal cover, a portal frame, a surface adjacent to a portal,and a surface adjacent to a portal cover.

A motion sensor detects movement of the security device. A motion sensordetects physical stimulus, physical quantities, physicalcharacteristics, and/or a change in a physical quantity orcharacteristic. A motion sensor may detect a physical stimulus that isdifferent from the physical stimulus detected by a removal detector. Amotion sensor may detect an event. A motion sensor may report an event.An event may include motion greater than a threshold and vibrationwithin a frequency range. A motion sensor includes any conventionalmotion and/or vibration sensor. An implementation of security device 100includes a motion sensor that includes a piezo film strip.

Access control may receive event notices, apply policy for warningaction, apply policy for a response to authorized and/or unauthorizedaccess, and assist in event detection. Event notices may be reported tothe access control from any sensor, detector, user (e.g., panic button),or system operator (e.g., system test). Access control may include anyconventional data processing equipment, communication equipment, sensingequipment, and software. Assisting in event detection may includereceiving physical stimulus, physical quantities, and/or physicalcharacteristics from a sensor and/or detector to detect a change.Applying policy may include receiving user information, transmittinguser information to a central location, receiving stored userinformation, transmitting stored user information, comparing userinformation to stored information, reporting authentication status(e.g., failed, successful), and determining a response to unauthorizedaccess.

A communication module communicates with other units of a securitysystem. Units of a security system may include security devices asdescribed herein, an aggregator that aggregate information from aplurality of security devices, and a central location (e.g., manned,unmanned). A communication module communicates using any conventionalhardware (e.g., wired, wireless) and any conventional protocol (e.g.,TCP/IP, 802.11, Zigbee, cellular telephone). A communication modulereceives and/or transmits information. Information may include reports,event notices, policy, actions taken according to policy, userinformation, stored information, physical stimulus detected, physicalquantities detected, physical characteristics detected, and/or a changein a physical quantity or characteristic detected.

Access control may use information received by the communication module.Access control may transmit information to another unit using thecommunication module.

An implementation of security device 100 may include portal sensor 102,removal detector 104, motion sensor 106, access control 110, andcommunication module 112.

Removal detector 104 may include bias device 206, sensor 202, andcomparator 204.

A sensor detects physical stimulus, physical quantities, physicalcharacteristics, and/or a change in a physical quantity orcharacteristic. A sensor may detect indicia of removal. A sensor mayinclude any conventional sensing equipment and software. For example,sensor 202 may include a magnetic flux sensor (e.g., Hall effect sensor,a magnetometer, a gaussmeter), vibration sensors, current sensors,voltage sensors, light sensors, location sensors (e.g., GPS), and motionsensor (e.g., field of view differencing detectors, illumination changedetectors, change of reflectivity detectors).

A bias device provides a physical stimulus of the type of physicalstimulus detected by the sensor. A bias device provides a base quantity(e.g., magnitude) of a physical stimulus. A sensor detects at least aportion of the base quantity. Environmental factors (e.g., proximity toa physical object, human activity, movement) may affect the quantity ofthe base stimulus detected by the sensor. Environmental factors mayincrease or decrease the quantity of the physical stimulus detected bythe sensor.

A comparator receives information regarding the quantity of the physicalstimulus detected by the sensor. A comparator may detect a thresholdchange in the quantity of the physical stimulus detected by the sensor.A comparator may apply a hysteresis to the information received from thesensor to reduce an effect that noise may have on the quantity of thephysical stimulus reported by the sensor. A comparator may provide anotice in accordance with detecting a threshold change in the quality ofphysical stimulus detected by the sensor. A notice may include avoltage, a current, and a data packet of a communication protocol. Athreshold may be adjusted. Adjustment includes increasing, decreasing,and maintaining a value of the threshold. An adjustment may be made inaccordance with temperature, age, duty cycle, and environmentalconditions.

In one implementation, bias device 206 includes magnets 310 and 312.Sensor 202 includes hall switch 314. Hall switch 314 includes acomparator having a threshold. Hall switch 314 provides an electricalsignal in accordance with a change in the magnitude of the magnetic fluxdetected by hall switch 314 greater than the threshold. Hall switch 314is positioned in such a manner that at least a portion of magnetic flux308 between a pole of magnet 310 and a pole of opposite polarity ofmagnet 312 conducts through hall switch 314. Magnetic flux 306 between apole of magnet 310 and a pole of opposite polarity of magnet 312conducts away from hall switch 314 through metal 304.

Movement of removal detector 104 to a position proximate to metalsurface 402 conducts magnetic flux 404 (e.g., at least a portion ofmagnetic flux 308) away from Hall switch 314. Hall switch 314 detects achange between the magnitude of the magnetic flux 308 and 404 thatconducts through hall switch 314. Hall switch 314 provides a signal inaccordance with detecting the change. Hall switch 314 may provide thesignal to access control 110. The signal provides indicia of a removalof removal sensor 104 from metal surface 402.

Removal detector 104 may couple to security device 100 in such a mannerthat movement of security device 100 results in detectable movement inremoval detector 104. The above implementation of removal detector 104may detect removal of removal device 104, and thus security device 100,from surface 402. Coupling removal detector 104 to security device 100and/or to metal surface 402 may include attaching with glue, securingwith a fastener, and coupling with magnetic force.

In one implementation, security device 100 includes metal 304 in body302. Magnets 310 and 312 magnetically couple to metal 304. Magnets 310and 312 may be further held in a position using structure related tobody 302 or metal plate 304. Structure may include walls, supports, andrecesses.

Hall switch 314 couples to security device 100. The coupling of Hallswitch 314 to security device 100 includes using a fastener andpositioning hall switch 314 in a bore in metal 304. Hall switch 314couples in such a manner that hall switch 314 does not move (e.g.,rotational movement, vertical movement, horizontal movement) withrespect to magnet 310 and magnet 312 as security device 100 moves.Accordingly, movement of security device 100 from a position away frommetal surface 402 to a position proximate (e.g., in contact) to metalsurface 402 does not change the position between hall switch 314, magnet310 and/or magnet 312. A spaced between sensor 202 and bias device 206may be potted to reduce movement between sensor 202 and bias device 206.

The physical stimulus provided by bias device 206 may further provide acoupling force. The coupling force may couple removal detector 104 tosecurity device 100 and/or to an object. As mentioned above, in oneimplementation, magnets 310 and 312 of removal detector 104 magneticallycouple to metal 304 of security device 100. Magnets 310 and 312 mayfurther magnetically couple security device 100 to metal surface 402.Coupling security device 100 to metal surface 402 conducts magnetic flux404 away from Hall switch 314. Removal of security device 100 from metalsurface 402 permits at least a portion of magnetic flux 308 to conductthrough Hall switch 314. Detection of a change in the magnitude of themagnetic flux through Hall switch 314 provides indicia of a removal oran attachment of security device 100 from/to metal surface 402.

Metal surface 402 may include a metal door, a door with a metal surface,a door having a metal portion, a metal portal cover, a surface adjacentto a portal.

An implementation of removal detector 104 includes u-shaped magnet 502and hall switch 506 positioned in the cavity of u-shaped magnet 502. Atleast a portion of magnetic flux 504 from a north pole and a south poleof magnet 502 conducts through hall switch 506. Placement of removaldetector 104 proximate to metal surface 602 conducts magnetic flux 604(e.g., at least a portion of magnetic flux 504) away from Hall switch506. Hall switch 506 detects a change between the magnitude of themagnetic flux 504 and 604. Hall switch 506 provides a signal inaccordance with detecting the change.

An implementation of removal detector 104 includes cylindrical magnet702 and hall switch 706 positioned in a cavity of magnet 702. At least aportion of magnetic flux 704 from a north pole and a south pole ofmagnet 702 conducts through Hall switch 706. Placement of removaldetector 104 proximate to a metal surface conducts at least a portion ofmagnetic flux 704 away from Hall switch 706. Hall switch 706 detects aconducting away of magnetic flux away from Hall switch 706 when removaldetector 104 is positioned proximate to a metal surface. Hall switch 706provides a signal in accordance with detecting a conducting away.

An implementation of security device 800 includes at least one ofremoval detectors 830 and 840. Magnets 806-822 provide a magnetic fluxthat conducts through hall switches 832 and 842. Magnets 810 and 820 mayprovide a primary magnetic flux that conducts through Hall switch 842.Magnets 806, 808, 812, 814, 816, and 822 may provide a secondarymagnetic flux that may increase or decrease the magnitude of themagnetic flux provided by magnets 810 and 820 and that conducts throughhall switch 842.

The poles of magnets 806-822 may be arranged to increase or decrease amagnetic flux that conducts through hall switch 832 and/or 842. Forexample, magnets 806-812 may be positioned such that their north polesare oriented in the same direction and the south poles of magnets814-822 are positioned opposite. Such an arrangement may increase amagnetic flux detected by hall switches 832 and 842 when security device800 is not proximate to a metal surface. The arrangement of magneticpoles shown in FIG. 8 may decrease a magnitude of magnetic flux detectedby hall switches 832 and 842 when security device 800 is not proximateto a metal surface.

Magnets 806-822 may further be used to mount removal detectors 832 and842 to body 802 of security device 800 and/or to a metal surface (notshown). In this implementation, magnets 806-822 magnetically couple tometal plate 804 of body 802. Hall switch 832 and 842 also couple to body802 in such a manner that hall switch 832 and 842 to not move withrespect to magnets 806-822. Placement of security device 800 proximateto a metal surface (not shown) magnetically couples security device 800to the metal surface and further conducts at least a portion of themagnetic flux of magnets 806-822 away from Hall switch 832 and 842.

A sensor may have a sensing axis. A sensing axis includes an axisthrough a sensor. Providing a physical stimulus along a sensing axis maypermit a sensor to have greater sensitivity in detecting a magnitude ofa physical stimulus. For example, sensor 902 is shown relative toorthogonal x, y, and z axes. A sensing axis of sensor 902 comprises thex-axis. Accordingly, detector 902 may detect a physical stimulusprovided along the x-axis while the same magnitude of a physicalstimulus provided along any other axis or direction may be detected to alesser extent or not at all.

In the case of a magnetic sensor, positioning the sensing axis relativeto a magnetic flux provided by a bias magnet may permit a magneticsensor to have greater sensitivity in detecting variations in amagnitude of the magnetic flux. Increased sensitivity enables sensor 202to detect smaller variations in the magnitude of the magnetic fluxand/or to be less immune to noise. A magnetic flux includes a flow ofmagnetic stimulus between poles of opposite polarity. For example, amagnetic flux flows between a north pole and a south pole (or visaversa) of magnets 312 and 310; magnet 502, magnet 702, magnets 810 and820 (not shown), and magnet 1004.

Positioning the sensing axis relative to a magnetic flux includespositioning the sensing axis perpendicular, parallel, and at an angle tothe magnetic flux. In an implementation, the sensing axis of Hall switch314 is positioned perpendicular to magnetic flux 308. In anotherimplementation, Hall switch 1006 is positioned perpendicular to magneticflux 1008. Magnet 1004 of removal detector 104 couples to body 1002 ofsecurity device 100. At least a portion of magnetic flux 1008 conductsthrough Hall switch 1006 when security device 100 is positioned awayfrom metal surface 1102. Magnetically coupling security device 100 tometal surface 1102 using magnet 1004 conducts magnetic flux 1104 (atleast a portion of magnetic flux 1008) away from Hall switch 1006. Hallswitch 1006 detects a change between the magnitude of the magnetic flux1008 and 1104. Hall switch 1006 provides a signal in accordance withdetecting the change.

Portal sensor 102 may include sensor 1202, bias device 1204, processor1206 and memory 1212. Sensor 1202 may include hall sensor 1302. Biasdevice 1204 may include magnet 1304.

Processor 1206 includes a conventional programmable controller circuithaving a microprocessor, memory, timer, and analog to digital converterprogrammed according to various aspects of the present invention, toperform methods discussed below. The microprocessor executes on a storedprogram and data. Portal sensor 102 may include process 1206 or methodsperformed by processor 1206 may be performed by a processor that alsoperforms methods for access control 110.

An implementation of portal sensor 102 includes Hall sensor 1302 andmagnet 1304. Magnet 1304 provides a magnetic flux. At least a portion ofthe magnetic flux from magnet 1304 conducts through Hall sensor 1302.Hall sensor 1304 provides indicia of a magnitude of a magnetic flux 1306that conducts through hall sensor 1302. Indicia of a magnitude of amagnetic flux includes a voltage proportional to a magnetic flux and acurrent proportional to a magnetic flux.

Hall sensor 1302 and magnet 1304 mount in body 1308 of security device100 in such a manner that movement of security device 100 and/or aportal does not move sensor 1302 with respect to magnet 1304.

Movement of portal sensor towards and/or away from a metal portion of aportal changes a magnitude of the magnetic flux (e.g., 1306, 1402) thatconducts through Hall sensor 1302. A magnitude of magnetic flux thatconducts through Hall sensor 1302 is proportional to a distance betweenbody 1308 of security device 100 and portal cover 1402. A portal coverincludes a metal door, a door having a metal portion, a door having ametal surface, and a window with a metal portion. Hall sensor 1302detects a magnitude of the magnetic flux through Hall sensor 1302. Hallsensor 1302 provides indicia of the magnitude of the magnetic flux toprocessor 1206 to perform methods described below.

Methods, discussed herein, performed by security device 100 may beperformed by any combination of initializing, reading, calculating,setting, and detecting capabilities of the available components of thesecurity device. Data used by security device 100 to perform methods maybe stored, retrieved, converted, averaged, summed, compared,transmitted, and displayed. Security device 100 may perform a functionin accordance with a result of performing a method. For example, portalsensor 102 may perform methods 1500 of FIG. 15. Some methods of 1500 maybe distributed to other components communicated by communication module112.

A dataflow diagram describes the cooperation of processes that may beimplemented by any combination of serial and parallel processing. In afully parallel implementation, an instance of each required process isinstantiated when new or revised data for that process is available; or,a static set of instances share processing resources in a single ormultithreaded environment, each process operating when new or reviseddata is available to that process.

Process 1500 may begin upon reset and/or power up of security device100. Process 1500 may also begin in accordance with a software commandexecuted by processor 1206 or through a process for exception handling.

Initializing process 1502 prepares data and components to perform theother processes of process 1500. Preparing data includes setting a datato an initial value. For example, setting element index to a firstelement of an array of elements for storing a series of prior sensorvalues; setting each element of the array of elements to an initialvalue; and setting sum and average value to zero. Preparing a componentincludes resetting analog-to-digital converter 1208, setting timer 1210to an initial value, establishing interrupt intervals for processor1206, and establishing interrupt vectors for processor 1206.

Initialization process 1502 may further establish a magnitude of amagnetic flux through sensor 1302 that represents a closed position of aportal cover.

Read sensor process 1504 receives data from sensor 1202. Data fromsensor 1202 includes indicia of a magnitude of a physical stimulusdetected by sensor 1202. For example, data from sensor 1202 may includeindicia of a magnitude of a magnetic flux conducted through sensor 1302.Data from sensor 1202 may be stored in data store 1512. For example,data read from sensor 1202 may be stored in a data referred to aspresent sensor value.

Calculate average process 1506 determines and average value of the datareceived from sensor 1202 with respect to prior data received fromsensor 1202. A data structure (e.g., array, linked list) may store priorsensor values. The data structure may be accessed using an elementindex. The number of elements in the data structure may be stored as adata referred to as number of elements. The present sensor value may becombined with the prior sensor values in such a manner as to produce asum of all values read from sensor 1202 up to the number of elements. Anaverage value of prior sensor values may be produced by dividing the sumby the number of valid values present in the prior sensor valuesstructure.

Data and intermediate values may be stored in data store 1512 andaccessed by processor 1206. Data store 1512 may be located in memory1212.

Calculating an average value may compensate for drift in the operationof components of portal sensor 102. For example, averaging a series ofvalues received from sensor 1202 may compensate for a drift in thevalues received from sensor 1202 over temperature and time (e.g., agingof sensor, bias device).

Set thresholds process 1508 establishes thresholds for use by otherprocesses. Thresholds may be used to determine whether to perform anaction. An action may include using data received from sensor 1202 toform an average, discarding data received from sensor 1202, and settingan alarm status (e.g., active, inactive, early warning). A thresholdincludes any threshold used by process 1500 to perform the processes ofsecurity device 100. For example, thresholds set by set thresholdprocess 1508 may include a drift threshold and an alarm threshold. Athreshold may include a single value, a series of values, and a valuehaving an upper boundary and a lower boundary.

An implementation of process 1500 uses a drift threshold and an alarmthreshold that each has an upper boundary and a lower boundaryrespectively. An average value of data received from sensor 1202 may becalculated in accordance with the drift threshold. For example, datareceived from sensor 1202 having a value that falls within the driftthreshold (e.g., greater or equal to a lower boundary, less than orequal to an upper boundary) is used to calculate an average value forsensor data as discussed above. Data received from sensor 1202 having avalue that falls outside the drift threshold (e.g., less than a lowerboundary, great than an upper boundary) is not used to calculate anaverage value.

An alarm status may be set in accordance with the alarm threshold. Forexample, data received from sensor 1202 having a value that falls withinthe alarm threshold (e.g., greater or equal to a lower boundary, lessthan or equal to an upper boundary) indicates movement of a portal coverwithin a limit, thus the alarm status may be set to inactive. Datareceived from sensor 1202 having a value that falls outside the alarmthreshold (e.g., less than a lower boundary, great than an upperboundary) indicates movement of a portal cover beyond a limit, thus thealarm status may be set to active. Data received from sensor 1202 havinga value that falls outside the alarm threshold followed by a subsequentvalue that falls within the alarm threshold or a pattern that fallswithin and outside the alarm threshold over a period of time may permitthe alarm status to be set to an early warning state.

Set thresholds process 1508 may set a threshold to compensate for driftin the operation of components of portal sensor 102. An implementationof portal sensor 102 sets threshold values in accordance with an averagevalue of the data received from sensor 1202.

An implementation of portal sensor 102 sets a drift threshold to accountfor noise (e.g., jitter, thermal, electrical, mechanical) thatinfluences detection by sensor 1202. An implementation of portal sensor102 sets the drift boundary as being equivalent to the six leastsignificant bits of analog-to-digital converter 1208.

An implementation of portal sensor 102 sets an alarm threshold to set alimit on portal movement. The limit is set in accordance with the rangeof motion detectable by sensor 1202.

Detect door status process 1510 detects a position of a portal cover.Detecting a position of a portal cover includes detecting movement of aportal cover outside of a limit. Detect door status process 1510 sets analarm status in accordance with detecting as discussed above. Forexample, as discussed above, a value received from sensor 1202 outsidethe alarm threshold indicates that the alarm status may be set toactive.

Any conventional computational techniques may be used to determinewhether a data value received from sensor 1202 falls within or outside athreshold (e.g., comparison to threshold values, rate of change, amountof change from previous value).

FIG. 16 represents an implementation of process 1500 including datavalues receive from sensor 1202 and values set for the drift and alarmthresholds. In FIG. 16, squiggly line 1602 represents a series ofpresent sensor values received from sensor 1202. Data from sensor 1202that falls within drift upper boundary 1604 and drift lower boundary1606 are used to calculate the average value of the data received fromsensor 1202. Datum 1608 from sensor 1202 falls outside of the driftthreshold and is not used to calculate an average value. Datum 1608falls within the alarm threshold. Active alarm status 1614 occurs whendata from sensor 1202 that falls outside the alarm threshold.

Line 1702 of FIG. 17 represents the average value of the values ofsquiggly line 1602 that falls within the drift threshold. The averagevalue does not change during the alarm active status because no datafrom sensor 1202, as depicted in FIG. 16, falls within the driftthreshold accordingly the average value does not change.

Security device 100 may couple to any object to detect removal. Securitydevice 100 may be positioned to detect movement of a portal cover. Inone implementation, security device 100 magnetically couples to rightportal cover 1804 and detects movement of adjacent left portal cover1806. Removal detector 104 magnetically couples body 1902 of securitydevice 100 to right portal cover 1804. Portal sensor 102 detectsmovement of left portal cover 1806 relative to security device 100 andthus right portal cover 1804. Movement of left portal cover 1806relative to right portal cover 1804 greater than a threshold may resultin a warning of unauthorized access. Removal of body 1902 from rightportal cover 1804 may result in a warning of unauthorized access.

Security device 100 may couple to and monitor a variety of portals. Forexample, a shape of the body of security device 100 may fit a particularportal construction. In one implementation, body 2002 of security device100 positions removal detector 104 and portal sensor 100 on each side ofseal 2008 between right portal cover 2004 and left portal cover 2006.

Portal sensor 102 and/or removal detector 104 may be moveably coupled tosecurity device 100. Moveably coupling portal sensor 102 and/or removaldetector 104 to the body of security device 100 permits security device100 to monitor portals having different closure mechanism, portalmounting mechanism, and portal spacing (e.g., gaps, misalignment). Amoveable coupling may provide security device 100 greater uniformity incoupling to a portal and detecting portal status. In one implementation,portal sensor 102 moves along track 2112. Track 2112 permits portalsensor 102 to retract into body 2102 when portal cover 2110 is flushwith portal casing 2106. Track 2112 permits portal sensor to extend frombody 2102 when portal cover 2110 is not flush with portal casing 2106 asshown in FIG. 21. A moveable coupling may permit greater movement of aportal or security device 100 before providing a notice.

Security device 100 may couple to a portal cover, a portal casing,and/or a surface adjacent to a portal using a fastener. A fastener maybe used in addition to or as a substitute to any couple force providedby removal detector 102. For example, fastener 2104 couples body 2102 ofsecurity device 100 to portal casing 2106. In an implementation whereremoval detector is of the type as removal detector 840, the removaldetector provides additional magnetic coupling to a portal casing 2106that is susceptible to magnetic coupling.

A portal that is not susceptible to magnetic coupling may be preparedfor magnetic coupling using fasteners that are susceptible to magneticcoupling. For example, a fastener that is susceptible to magneticcoupling may be coupled to a portal cover. Coupling the fastener to theportal cover includes mechanical coupling and chemical coupling (e.g.,glue). A fastener may be positioned on the portal cover to correspond toa position of a magnet in a removal detector. An implementation usesfastener 2206 coupled to right portal cover 2210 and positioned tocorrespond to the positions of magnets 2214 of removal detector 104.Fasteners 2206 mechanically couple to right portal cover 2210 andmagnets 2214 magnetically couple to fasteners 2206 thereby coupling body2202 of security device 100 to right portal cover 2210. Fasteners 2206are positioned in such a manner that coupling body 2202 to the fasteners206 positions portal sensor 102 proximate to left portal cover 2212.

Fasteners may also be used as conductors. A conductor may carry anelectric potential. An electric potential may be impressed (e.g.,provided) on a fastener by a first device and detected by a seconddevice and/or alternately provided and detected by the first and seconddevice. An electrical potential may carry information (e.g., signal). Afastener having an end portion exposed on each side of a portal covermay carry an electrical potential from one side of the portal through tothe other side of the portal. An electric potential includes a directcurrent (e.g., DC) potential and an alternating potential (e.g.,changing over time). In one implementation, fasteners 2206 conduct anelectrical potential between access control 110 and device 2216positioned in body 2204. Body 2204 is positioned on a different side ofportal 2206 than body 2202. Device 2216 may include a security device, aportion of a security device, a communication module, and aconcentrator. A fastener used as a conductor may need to be insulatedfrom the material of the portal cover. For example, metal fasteners needto be insulated from a metal door to permit the fasteners to carry asignal. In one implementation, insulator 2208 insulates fastener 2206from the material of right portal cover 2210.

Security device 100 may cooperate with a fastener to couple securitydevice 100 to a portal cover and/or portal frame. Cooperation mayinclude a coupling between the fastener and the portal and a couplingbetween the fastener and security device 100. A coupling between thefastener and security device 100 may permit portal sensor 102 ofsecurity device 100 to move between a sensing position to a non-sensingposition without decoupling the fastener from the portal cover and/orframe. A coupling between the fastener and security device 100 maypermit removal detector 104 to move between a removed position and anon-removed position without decoupling the fastener from the portalcover and/or frame. Movement from a non-removed position to a removedposition magnetically decouples security device 100 from the fastener,but not the fastener from the portal. In one implementation, fastener2302 includes base 2402 and a first portion 2304 of hinge 2308. Body2310 of security device 100 includes a second portion 2306 of hinge2308. Body 2310 pivotally moves with respect to fastener 2302 aroundhinge 2308.

Fastener 2302 includes first portion 2304 of hinge 2308, base 2402, andsurface 2404. Base 2402 couples to right portal cover 2312. Coupling ofbase 2402 to right portal cover 2312 includes mechanical (e.g.,fastener, welding), magnetic, and chemical (e.g., glue). When body 2310of security device 100 is positioned in an operable position, surface2404 is positioned adjacent to removal detector 102. Surface 2404 may beformed of a material that is susceptible to magnetic forces to cooperatewith a magnetic implementation of removal detector 102. A magneticimplementation of removal detector 102 may magnetically couple tosurface 2404 and detect removal of security device from surface 2404.

A security device 100 that cooperates with fastener 2302 includes secondportion 2306 of hinge 2308, removal detector 104 that cooperates withsurface 2404, and portal sensor 102 that is positioned adjacent to leftportal cover 2314 when body 2310 of security device 100 is positioned inan operative position. Portal sensor 102 may include additional magnets2502 to nominally couple portal sensor 102 to left portal cover 2314.Magnets 2502 may increase, decrease, or have no affect on a magnitude ofthe magnetic flux detected by sensor 1202. Magnets 2502 may increase aamount of force required to move left portal cover 2314 beyond a limit.

A shape of a fastener may cooperate with a portal to attach to anyportion of a portal. For example, referring to FIG. 26, fastener 2602couples to right portal cover 2312 over handle 2316. Body 2610 ofsecurity device 100 couples to fastener 2602 at hinge 2608 in such amanner that removal detector 102 (not shown) of security device 100 ispositioned adjacent to surface 2606 and portal sensor 102 (not shown) ispositioned adjacent to left portal cover 23 14. Base 2604 couples toright portal cover 2312.

The foregoing description discusses preferred embodiments of the presentinvention which may be changed or modified without departing from thescope of the present invention as defined in the claims. While for thesake of clarity of description, several specific embodiments of theinvention have been described, the scope of the invention is intended tobe measured by the claims as set forth below.

1. A security device that detects movement of a provided portal cover,the security device comprising: a sensor that provides indicia of amagnitude of a magnetic flux through the sensor; a bias magnet thatprovides the magnetic flux through the sensor; a processor that detectsa change in the magnitude of the magnetic flux outside an upper boundaryand a lower boundary of a first threshold and a second thresholdrespectively; wherein: the sensor does not move with respect to themagnet; movement between the sensor and the portal cover changes themagnitude of the magnetic flux through the sensor; the processordetermines an average value of a series of values of the indicia of themagnitude of the magnetic flux that fall within the upper boundary andthe lower boundary of the first threshold; the upper boundary and thelower boundary of the first threshold and the second thresholdrespectively are set in accordance with the average value.
 2. Thesecurity device of claim 1 wherein the processor provides a notice inaccordance with the change in the magnitude of the magnetic flux thatfalls outside the upper boundary and the lower boundary of the secondthreshold.
 3. The security device of claim 1 wherein: the sensorcomprises a sensing axis; and the bias magnet provides the magnetic fluxparallel to the sensing axis.
 4. The security device of claim 1 whereinthe average value comprises only the indicia of the magnitude that fallbetween the lower boundary and the upper boundary of the firstthreshold.
 5. The security device of claim 1 wherein the indiciacomprises a voltage.
 6. The security device of claim 1 wherein theindicia comprises a current.
 7. The security device of claim 1 whereinthe sensor couples to the security device and is positioned adjacent tothe portal cover.
 8. The security device of claim 1 wherein the magnetcouples to the security device distal from the portal cover along anaxis between the sensor and the magnet.
 9. The security device of claim1 wherein the absolute value of the upper boundary and the lowerboundary of the first threshold and the second threshold respectivelyare different.
 10. The security device of claim 1 wherein the absolutevalue of the upper boundary and the lower boundary of the firstthreshold are less than the absolute value of the upper boundary and thelower boundary of the second threshold.
 11. The security device of claim1 wherein the series of values comprises at least one thousand values.12. The security device of claim 1 wherein the processor receivesindicia of the magnitude at least every 0.5 seconds.
 13. The securitydevice of claim 1 wherein the processor comprises an analog-to-digitalconverter that converts a voltage.
 14. A method performed by a securitydevice for detecting movement of a portal cover, the method comprising:averaging a series of values of indicia of a magnitude of a magneticflux through a sensor that fall within an upper and a lower boundary ofa first threshold to provide an average value; detecting indicia themagnitude of the magnetic flux that falls outside an upper and a lowerboundary of a second threshold; adjusting the upper and the lowerboundary of the first threshold and the second threshold respectively inaccordance with the average value; providing a signal in accordance withdetecting; wherein: a magnet couples to a body of the security device toprovide the magnetic flux through the sensor; the sensor couples to thebody; the sensor does not move with respect to the magnet; movement ofthe sensor with respect to the portal cover changes the magnitude of themagnetic flux through the sensor.
 15. The method of claim 14 whereinaveraging comprises detecting whether a current indicia of the magnitudeof the magnetic flux is less than the upper boundary and greater thanthe lower boundary of the first threshold.
 16. The method of claim 14wherein averaging comprises eliminating each indicia that falls outsidethe upper boundary and the lower boundary of the first threshold. 17.The method of claim 14 wherein averaging comprises eliminating eachindicia that falls outside the upper boundary and the lower boundary ofthe second threshold.
 18. The method of claim 14 wherein adjustingcomprises changing a value of the upper boundary and the lower boundaryof the first threshold in accordance with a change in the average value.19. The method of claim 14 wherein adjusting comprises changing a valueof the upper boundary and the lower boundary of the second threshold inaccordance with a change in the average value.
 20. The method of claim14 wherein the absolute value of the upper boundary and the lowerboundary of the first threshold are less than the absolute value of theupper boundary and the lower boundary of the second threshold.